my $flush = 0;
my @suits = ( "D", "S", "C", "H" );
my $long_hand = ("2H 3D 4C 5S 5H)";

# Method 1:  43 microseconds
#    (My initial code ... seemed slow ... ergo benchmark)
foreach ( @suits ) {
    @m = ( $long_hand =~ m/$_/g );
    $flush = 1 if  ($#m eq 4 );
}

# Method 2: 126 microseconds (definitely bottleneck)
foreach ( @suits ) {
    my $count = ( eval "\$long_hand =~ tr/$_//" );
    $flush = 1 if  ($count eq 5 );
}

#Method 3: accounts for only 3(!) microseconds of code
# Ugly but functional for very few patterns to check
# BUT what if I had 10k patterns to check
$flush = 1 if ( $long_hand =~ tr/D// eq 5);
$flush = 1 if ( $long_hand =~ tr/S// eq 5);
$flush = 1 if ( $long_hand =~ tr/C// eq 5);
$flush = 1 if ( $long_hand =~ tr/H// eq 5);