There are three ways that I know of to call a sub as a variable. You can store a pointer to an anonymous function in a variable and call that, but I dont think this is what you are looking for. You can also store the proper function name in a variable can call it by just prepending a '&' on the front like

$var = 'funcname';
&$var();
sub funcname { print "Hello\n" }
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But this will not work if you are using 'strict', so here are the three ways you can do it that will work with strict.

use strict;

#
# create an anonymous function
#
my $func = sub { print "Sub Anonymous\n" };

#
# create named sub
#
sub funcname { print "Sub funcname\n" }


#
# call anonymous subroutine
#
&$func();

my $mysub = 'funcname';

#
# call subroutine but only with no strict references
#
no strict 'refs';
&$mysub();
use strict;

#
# or call with eval statement
#
eval('&'.$mysub.'()');

#
# catch error from eval statement
#
if( $@ )
{
    warn($@);
}
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The first one is just an anonymous subroutine, and the next two are calling a name subroutine referenced in a variable. By turning off 'strict refs' you run the risk of getting a crtitical run time error if there is no function named in $mysub. So it is probably better to use the eval and catch the error. That will prevent the program from critically failing if the function does not exist.