sub mysub { print "mysub $_[0]\n"; }; 
my $s="mysub"; 
&{$s}( "toto");                         # This is what you want

##</code><code>##

my %h=( mysub1 => \&mysub_1,  # \&mysub_1 is a reference to the subroutine
        mysub2 => \&my_sub_2);
my $s="mysub1";               # or however you get the string 

if( $h{$s})
  { $h{$s}->( "toto"); }     # this is how you call the subroutine with its arguments
else
  { die "wrong sub called: $s"; }

sub mysub_1 { print "mysub 1 $_[0]\n"; }; 
sub mysub_2 { print "mysub 2 $_[0]\n"; };