Re^5: perl indication of end of string already matched

BTW: Another way to determine the start/middle/end position of a matched substring in a string is by using the @- @+ regex special variables; see perlvar.

c:\@Work\Perl\monks>perl -wMstrict -le
"my $s = 'foo--bar--baz';
 ;;
 while ($s =~ m{ (\w+) }xmsg) {
   printf qq{matched '$1' %s of '$s' \n},
     $-[1] == 0         ? 'at start'  :
     $+[1] == length $s ? 'at very end' :
                          'in middle';
   }
"
matched 'foo' at start of 'foo--bar--baz'
matched 'bar' in middle of 'foo--bar--baz'
matched 'baz' at very end of 'foo--bar--baz'
[download]

Play with adding '-'s at the start/end of $s to convince yourself this works.

Give a man a fish: <%-{-{-{-<

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Re^6: perl indication of end of string already matched (updated) by haukex (Archbishop) on Jun 09, 2020 at 08:29 UTC
Good point, although in this case those variables also don't allow one to differentiate between the last two matches: `$ perl -MData::Dump -e '$a="abc";for(1..6){ $a=~m/.\|$/g; dd \@-,\@+ }' ([0], [1]) ([1], [2]) ([2], [3]) ([3], [3]) ([3], [3]) ([0], [1])` [download] Update: Hmm, well they can if one adds capture groups, which is kind of the same workaround as I showed here. `$ perl -MData::Dump -e '$a="abc";for(1..6){$a=~m/(.\|$)/g; dd \@-,\@+}' ([0, 0], [1, 1]) ([1, 1], [2, 2]) ([2, 2], [3, 3]) ([3, 3], [3, 3]) ([3], [3, 3]) ([0, 0], [1, 1])` [download]	[reply] [d/l] [select]

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Re^6: perl indication of end of string already matched (updated)
by haukex (Archbishop) on Jun 09, 2020 at 08:29 UTC

Good point, although in this case those variables also don't allow one to differentiate between the last two matches:

$ perl -MData::Dump -e '$a="abc";for(1..6){ $a=~m/.|$/g; dd \@-,\@+ }'
([0], [1])
([1], [2])
([2], [3])
([3], [3])
([3], [3])
([0], [1])
[download]

Update: Hmm, well they can if one adds capture groups, which is kind of the same workaround as I showed here.

$ perl -MData::Dump -e '$a="abc";for(1..6){$a=~m/(.|$)/g; dd \@-,\@+}'
([0, 0], [1, 1])
([1, 1], [2, 2])
([2, 2], [3, 3])
([3, 3], [3, 3])
([3], [3, 3])
([0, 0], [1, 1])
[download]

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