I am not sure if i completely understand the spec. Here is my shot at this. I have put the data at the end so you can see if it is structured in that way.

#!/usr/bin/perl -w

use strict;

# open(DATA,"file.txt") or die $!;  # I am using DATA handle but you c
+an open a file to read contents too.

my %functions;
while (<DATA>) {
    chomp;
    my @functxt = ();
    my $desc = ();
    if (/STANDARD/)    {
        @functxt = split /\s+/;
        $desc = <DATA>;
        $functions{pop(@functxt)} = $desc;    # assuming last word is 
+function name
    }
}

print +($_, " : ", $functions{$_}, $/) for (keys %functions); 
__DATA__
# STANDARD func1 
func1 does something funny
blah
blah
ok
junk text
# STANDARD func2 
func2 does something useful

# STANDARD func3 
func3 is a math function
[download]

output

func1 : func1 does something funny        
func3 : func3 is a math function                                
func2 : func2 does something useful
[download]