untested:

my @candidates = qw(
  http://www.someplace.com/foo
  http://www.someplace.com/foo/bar
  http://www.someplace.else.com/foo
);

my $target = 'http://www.someplace.com/foo/fighter/index.html';
my %leader = ( uri => '', length => 0 );

foreach my $candidate (@candidates) {

    if( $target =~ /^$candidate/ ) {

        if( length($candidate) > $leader{length} ) {

            @leader{'uri','length'} = 
                ($candidate,length($candidate));
        }
    }
}

if( $leader{uri} ) {

    print $leader{uri},',',substr($target,$leader{length});
}
else {

    print "no matches"
}
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