Regular Expressions 101

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`
^(?P<major>0|[1-9]\d*)\.(?P<minor>0|[1-9]\d*)\.(?P<patch>0|[1-9]\d*)(?:-(?P<prerelease>(?P<stage>(?:alpha|beta|rc))(?:\.(?P<feature>(?:(?P<pic>[0-9a-zA-Z-]*)\.)?[0-9a-zA-Z-]*))?))?(?:\+(?P<buildmetadata>[0-9a-zA-Z-]+(?:\.[0-9a-zA-Z-]+)*))?$
`
gm
^ asserts position at start of a line
Named Capture Group major
(?P<major>0|[1-9]\d*)
1st Alternative
0
0 matches the character 0 with index 4810 (3016 or 608) literally (case sensitive)
2nd Alternative
[1-9]\d*
Match a single character present in the list below
[1-9]
1-9 matches a single character in the range between 1 (index 49) and 9 (index 57) (case sensitive)
\d
matches a digit (equivalent to [0-9])
* matches the previous token between zero and unlimited times, as many times as possible, giving back as needed (greedy)
\. matches the character . with index 4610 (2E16 or 568) literally (case sensitive)
Named Capture Group minor
(?P<minor>0|[1-9]\d*)
1st Alternative
0
0 matches the character 0 with index 4810 (3016 or 608) literally (case sensitive)
2nd Alternative
[1-9]\d*
Match a single character present in the list below
[1-9]
1-9 matches a single character in the range between 1 (index 49) and 9 (index 57) (case sensitive)
\d
matches a digit (equivalent to [0-9])
* matches the previous token between zero and unlimited times, as many times as possible, giving back as needed (greedy)
\. matches the character . with index 4610 (2E16 or 568) literally (case sensitive)
Named Capture Group patch
(?P<patch>0|[1-9]\d*)
1st Alternative
0
0 matches the character 0 with index 4810 (3016 or 608) literally (case sensitive)
2nd Alternative
[1-9]\d*
Match a single character present in the list below
[1-9]
1-9 matches a single character in the range between 1 (index 49) and 9 (index 57) (case sensitive)
\d
matches a digit (equivalent to [0-9])
* matches the previous token between zero and unlimited times, as many times as possible, giving back as needed (greedy)
Non-capturing group
(?:-(?P<prerelease>(?P<stage>(?:alpha|beta|rc))(?:\.(?P<feature>(?:(?P<pic>[0-9a-zA-Z-]*)\.)?[0-9a-zA-Z-]*))?))?
? matches the previous token between zero and one times, as many times as possible, giving back as needed (greedy)
- matches the character - with index 4510 (2D16 or 558) literally (case sensitive)
Named Capture Group prerelease
(?P<prerelease>(?P<stage>(?:alpha|beta|rc))(?:\.(?P<feature>(?:(?P<pic>[0-9a-zA-Z-]*)\.)?[0-9a-zA-Z-]*))?)
Named Capture Group stage
(?P<stage>(?:alpha|beta|rc))
Non-capturing group
(?:alpha|beta|rc)
1st Alternative
alpha
alpha
matches the characters alpha literally (case sensitive)
2nd Alternative
beta
beta
matches the characters beta literally (case sensitive)
3rd Alternative
rc
rc
matches the characters rc literally (case sensitive)
Non-capturing group
(?:\.(?P<feature>(?:(?P<pic>[0-9a-zA-Z-]*)\.)?[0-9a-zA-Z-]*))?
? matches the previous token between zero and one times, as many times as possible, giving back as needed (greedy)
\. matches the character . with index 4610 (2E16 or 568) literally (case sensitive)
Named Capture Group feature
(?P<feature>(?:(?P<pic>[0-9a-zA-Z-]*)\.)?[0-9a-zA-Z-]*)
Non-capturing group
(?:(?P<pic>[0-9a-zA-Z-]*)\.)?
? matches the previous token between zero and one times, as many times as possible, giving back as needed (greedy)
Named Capture Group pic
(?P<pic>[0-9a-zA-Z-]*)
Match a single character present in the list below
[0-9a-zA-Z-]
* matches the previous token between zero and unlimited times, as many times as possible, giving back as needed (greedy)
0-9 matches a single character in the range between 0 (index 48) and 9 (index 57) (case sensitive)
a-z matches a single character in the range between a (index 97) and z (index 122) (case sensitive)
A-Z matches a single character in the range between A (index 65) and Z (index 90) (case sensitive)
- matches the character - with index 4510 (2D16 or 558) literally (case sensitive)
\. matches the character . with index 4610 (2E16 or 568) literally (case sensitive)
Match a single character present in the list below
[0-9a-zA-Z-]
* matches the previous token between zero and unlimited times, as many times as possible, giving back as needed (greedy)
0-9 matches a single character in the range between 0 (index 48) and 9 (index 57) (case sensitive)
a-z matches a single character in the range between a (index 97) and z (index 122) (case sensitive)
A-Z matches a single character in the range between A (index 65) and Z (index 90) (case sensitive)
- matches the character - with index 4510 (2D16 or 558) literally (case sensitive)
Non-capturing group
(?:\+(?P<buildmetadata>[0-9a-zA-Z-]+(?:\.[0-9a-zA-Z-]+)*))?
? matches the previous token between zero and one times, as many times as possible, giving back as needed (greedy)
\+ matches the character + with index 4310 (2B16 or 538) literally (case sensitive)
Named Capture Group buildmetadata
(?P<buildmetadata>[0-9a-zA-Z-]+(?:\.[0-9a-zA-Z-]+)*)
Match a single character present in the list below
[0-9a-zA-Z-]
+ matches the previous token between one and unlimited times, as many times as possible, giving back as needed (greedy)
0-9 matches a single character in the range between 0 (index 48) and 9 (index 57) (case sensitive)
a-z matches a single character in the range between a (index 97) and z (index 122) (case sensitive)
A-Z matches a single character in the range between A (index 65) and Z (index 90) (case sensitive)
- matches the character - with index 4510 (2D16 or 558) literally (case sensitive)
Non-capturing group
(?:\.[0-9a-zA-Z-]+)*
* matches the previous token between zero and unlimited times, as many times as possible, giving back as needed (greedy)
\. matches the character . with index 4610 (2E16 or 568) literally (case sensitive)
Match a single character present in the list below
[0-9a-zA-Z-]
+ matches the previous token between one and unlimited times, as many times as possible, giving back as needed (greedy)
0-9 matches a single character in the range between 0 (index 48) and 9 (index 57) (case sensitive)
a-z matches a single character in the range between a (index 97) and z (index 122) (case sensitive)
A-Z matches a single character in the range between A (index 65) and Z (index 90) (case sensitive)
- matches the character - with index 4510 (2D16 or 558) literally (case sensitive)
$ asserts position at the end of a line
Global pattern flags
g modifier: global. All matches (don't return after first match)
m modifier: multi line. Causes ^ and $ to match the begin/end of each line (not only begin/end of string)
Your regular expression does not match the subject string.

Regular Expression
No Match

`
`
gm

Test String