Because you're using the  /g regex modifier for all matches, the string match position never resets to the start of the string, but advances for each and every match performed. (Update: I should have written: advances for each and every successful match performed.) 

c:\@Work\Perl\monks>perl -wMstrict -le
"my $s = 'xx111yy22xx333yy44zz555xx666';
 ;;
 print qq{first capture: '$1'} if $s =~ m{ (\d+) }xmsg;
 ;;
 print qq{subsequent captures: '$1'} while $s =~ m{ (\d+) }xmsg;
"
first capture: '111'
subsequent captures: '22'
subsequent captures: '333'
subsequent captures: '44'
subsequent captures: '555'
subsequent captures: '666'

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The fact that the first match in the OPed code is a negative | negated match (so no action is taken) does not matter; it's still a  /g match against the same string. Eliminating the  /g modifier on the first match will cause string match position to be reset before subsequent matches (which must still use /g).

Note that use of the  /g modifier in an
    if ($string =~ m{ ... }xmsg) { ... }
statement is useless except as a way to introduce exactly the behavior you are seeing!

Update: A number of incremental updates made.

Give a man a fish:  <%-(-(-(-<

In reply to Re: A regex question. by AnomalousMonk
in thread A regex question. by FeistyLemur

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