Regular Expressions 101

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/
(?<dia>\d{2})-(?<mes>\d{2})-(?<ano>\d{4})
/
gm
Named Capture Group dia
(?<dia>\d{2})
\d
matches a digit (equivalent to [0-9])
{2} matches the previous token exactly 2 times
- matches the character - with index 4510 (2D16 or 558) literally (case sensitive)
Named Capture Group mes
(?<mes>\d{2})
\d
matches a digit (equivalent to [0-9])
{2} matches the previous token exactly 2 times
- matches the character - with index 4510 (2D16 or 558) literally (case sensitive)
Named Capture Group ano
(?<ano>\d{4})
\d
matches a digit (equivalent to [0-9])
{4} matches the previous token exactly 4 times
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.Try launching the debugger to find out why.

Regular Expression
No Match

/
/
gm

Test String