How does this compare speed-wise: 
>perl -wMstrict -le
"my @suits = qw(D S C H);
 my $suits = join '', @suits;
 my $flush = qr{ ([$suits]) (?: [^$suits]+ \1){4} }xms;
 print $_, $_ =~ $flush ? ' flush' : ' nope'
   for '2H 3D 4C 5S 5H', '1H 2H 3H 4H 5H';
"
2H 3D 4C 5S 5H nope
1H 2H 3H 4H 5H flush

[download]
Update: Might be faster if possessive: 
>perl -wMstrict -le
"my @suits = qw(D S C H);
 my $suits = join '', @suits;
 my $flush = qr{ ([$suits]) (?: (?> [^$suits]+) \1){4} }xms;
 print $_, $_ =~ $flush ? ' flush' : ' nope'
   for '2H 3D 4C 5S 5H', '1H 2H 3H 4H 5H';
"
2H 3D 4C 5S 5H nope
1H 2H 3H 4H 5H flush

[download]
5.10 has possessive modifier: 
>perl -wMstrict -le
"my @suits = qw(D S C H);
 my $suits = join '', @suits;
 my $flush = qr{ ([$suits]) (?: [^$suits]++ \1){4} }xms;
 print $_, $_ =~ $flush ? ' flush' : ' nope'
   for '2H 3D 4C 5S 5H', '1H 2H 3H 4H 5H';
"
2H 3D 4C 5S 5H nope
1H 2H 3H 4H 5H flush

[download]
Bugfix: Changed  (?> [^$suits])+ to  (?> [^$suits]+) per ikegami Re^6: Simple Matching.

In reply to Re^5: Simple Matching by AnomalousMonk
in thread Simple Matching by rnroot

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