This might do what you want:

#!/usr/bin/perl
use strict;
use warnings;
my $match = '1995_Olga_goes_to_Egypt';
my @pictures = qw{1996/1996_Olga_goes_to_Egypt/QD0017005.JPG 1995/1995
+_Olga_first_time_in_Cyprus/06330004.JPG
1995/1995_Olga_goes_to_Egypt/QD0017004.JPG};
my $picture;
foreach (sort @pictures) {
    print "Debug: $_\n";
    if (m/$match/)
    {
      print "Matched, $_\n";
      $picture = $_;
      last;
    }
}
print "Result: $picture\n";
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This assigns only the first matched element of @pictures to the lexical my $picture before dropping out of the loop.