Indeed, as has been mentioned:

use List::Util qw( first );

my $picture = first { /$match/ } sort @pictures;
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Without List::Util, I’d use a while:

my $picture = do {
    my @candidate = sort @pictures;
    shift @candidate while @candidate and $candidate[0] !~ /$match/;
    shift @candidate;
};
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After all, you need a temporary array to store the sorted list anyway – so you can afford to iterate it destructively, and thus you get to use while( @list ), which lets you get away without much synthetic index fiddling.

Update: fixed wrong sigil on 2nd shift; thanks, Tanktalus.

Makeshifts last the longest.