my $text = "foo";
sub SUBSTR {
    my $c = substr $text, 0, 1;
    return ( $c eq "*" or $c eq " " or $c eq "\t" or $c eq "\r" or $c eq "\n" );
}
sub REGEX {
    return ($text =~ m/^\*/ || $text =~ m/^\s+/);
}
use Benchmark;
timethese(5000000, { substr => \&SUBSTR, regex => \&REGEX })
__END__
Benchmark: timing 5000000 iterations of regex, substr...
     regex:  2 wallclock secs ( 1.07 usr +  0.00 sys =  1.07 CPU) @ 4672897.20/s (n=5000000)
    substr:  1 wallclock secs ( 1.38 usr +  0.00 sys =  1.38 CPU) @ 3623188.41/s (n=5000000)