Regular Expressions 101

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/
((?:ithelpdesk(?:|\d+)|deskserverithelp|itservicedeskhelp|ithelpservice(?:|\d+))@gmail.com)
/
igm
1st Capturing Group
((?:ithelpdesk(?:|\d+)|deskserverithelp|itservicedeskhelp|ithelpservice(?:|\d+))@gmail.com)
Non-capturing group
(?:ithelpdesk(?:|\d+)|deskserverithelp|itservicedeskhelp|ithelpservice(?:|\d+))
1st Alternative
ithelpdesk(?:|\d+)
ithelpdesk
matches the characters ithelpdesk literally (case insensitive)
Non-capturing group
(?:|\d+)
1st Alternative null, matches any position
2nd Alternative
\d+
\d
matches a digit (equivalent to [0-9])
+ matches the previous token between one and unlimited times, as many times as possible, giving back as needed (greedy)
2nd Alternative
deskserverithelp
deskserverithelp
matches the characters deskserverithelp literally (case insensitive)
3rd Alternative
itservicedeskhelp
itservicedeskhelp
matches the characters itservicedeskhelp literally (case insensitive)
4th Alternative
ithelpservice(?:|\d+)
ithelpservice
matches the characters ithelpservice literally (case insensitive)
Non-capturing group
(?:|\d+)
1st Alternative null, matches any position
2nd Alternative
\d+
\d
matches a digit (equivalent to [0-9])
+ matches the previous token between one and unlimited times, as many times as possible, giving back as needed (greedy)
@gmail
matches the characters @gmail literally (case insensitive)
. matches any character (except for line terminators)
com
matches the characters com literally (case insensitive)
Global pattern flags
i modifier: insensitive. Case insensitive match (ignores case of [a-zA-Z])
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

/
/
igm

Test String

Substitution

Processing...