use strict;
use warnings;

my $dataline = <<'DATALINE';
#something
$$$$
line1
#something
$$$$
line2
DATALINE

    my $dataline02 = $dataline;
    my $newval = 'name';
    
    pos($dataline) = 0;
    while($dataline =~ /\${4}\n(\w+)\d/g){
        $dataline02 =~ s/$1/$newval/;
    }
    
    print $dataline,"\n",$dataline02;