Something like this ?

#!/usr/bin/perl

use strict; # https://perlmonks.org/?node_id=11125451
use warnings;

sub indent {
    my $text = shift;
    $text =~ s/^\s//gm until $text =~ /^\S/m;
    return $text;
}

if (1) {
    print indent(<<"");
    Here is
    some test text
    with plenty of space
        and even an indented line
    at the start

}
[download]

Outputs:

Here is
some test text
with plenty of space
    and even an indented line
at the start
[download]