You're probably after an symbolic reference, and were almost but not quite there with your snippet...

sub function_1 { print "One\n" }
sub function_2 { print "Two\n" }

{     # Allow symbol table manipulation.
      # You do use strict;, right? :)
    no strict 'refs';

    foreach my $no ( 1 .. 2 ) {
        &{ "function_$no" }; # <--- THIS THING
    }
}
[download]

... but that could potentially blow up in your face if $no turned out to be something unexpected unless you wrapped the whole shebang inside an eval or made good use of can.

The more preferable (and use strict;-happy) way of doing this sort of thing is using something called a dispatch table, which'd look something like ...

sub function_1 { print "One\n" }
sub function_2 { print "Two\n" }

my %functions = (
    'DEFAULT' => sub { print "Huh?\n" },
    1         => \&function_1,
    2         => \&function_2,
);

foreach my $no ( 1 .. 3 ) {
    $no = 'DEFAULT' unless exists $functions{$no};

    $functions{$no}->();
}
[download]

    --k.