Hello choroba,

Thanks for the explanation, and I’m sorry to be obtuse but — I still don’t understand. :-( Consider:

#! perl -l
use strict;
use warnings;

my $s = 'uvXYZdabcXYZfg';

while ($s =~ /(\w\w\w)*?(XYZ)/g)
{
    print 'Found match ', $1, $2, ' at pos: ', pos $s;
}

print '-----';

while ($s =~ /(abc)*?(XYZ)/g)
{
    print 'Found match ', $1, $2, ' at pos: ', pos $s;
}

[download]

Output:

22:35 >perl 1476_SoPW.pl
Found match abcXYZ at pos: 12
-----
Use of uninitialized value $1 in print at 1476_SoPW.pl line 28.
Found match XYZ at pos: 5
Found match abcXYZ at pos: 12

22:35 >

[download]

The first capture in each regex is 3 characters wide, but the first regex matches only the second occurrence of XYZ whereas the second regex also matches the first occurrence, with (abc)*? matching zero times. Why the difference in behaviour? In particular, why does (\w\w\w)*? not also match zero times?

Athanasius <°(((>< contra mundum Iustus alius egestas vitae, eros Piratica,

In reply to Re^9: Understanding a portion of perlretut by Athanasius
in thread Understanding a portion on the Perlretut by BlueStarry

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