#!/usr/bin/perl -w
#
# replace_in_tree replaces stringx by stringy in files from current di
+rectory
# recursiveley and backups the original files to *.bak like
# find . -type f | xargs -n 255 perl -pi.bak -e 's/string x/string y/g
+'
# does.
#
# Author : Sascha Wuestemann
# License: Artistic GPL
# eMail  : Sascha.Wuestemann@epost.de
 
use strict;
 
sub usage {
print <<EOF;
 
usage:
 
replace_in_tree <to_be_replaced> <replacement> <filematcher>
 
replaces the string "to_be_replaced" with "replacement"
from the current directory downwards the filetree
in files matching filematcher, e.g. "*" or "*.html"
 
example:
 
replace_in_tree "Author: Bill Gates" "Author: Larry Wall" *.html
 
EOF
}
 
sub exec_replace {
open(GUN,"find . -name \"$ARGV[2]\" -type f | xargs -n 255 perl -pi.ba
+k -e 's/$ARGV[0]/$ARGV[1]/g'|")|| die "can't execute shell commands:$
+!\n";
close(GUN)|| warn "couldn't close shell:$!\n";
}
 
if (not $ARGV[2]) {
     usage;
     exit;
}
else {
     exec_replace
}
exit;
[download]

I think you are right: It's silly to execute this shell pipeline in a perl script.
And the way you do it is even worse.

If you want to put a complex shell command in a script, use a shell script, that's what it was made for.

If you just want to execute a shell command in a perl script, use the system command. Unless you need the output of the command, then use backticks.

Here is an example of a shell script doing the same as your perl script, but with much less resources:

#!/bin/sh

if [ $# -lt 3 ]; then
echo "
usage:

replace_in_tree <to_be_replaced> <replacement> '<filematcher>'
replaces the string "to_be_replaced" with "replacement"
from the current directory downwards the filetree
in files matching filematcher, e.g. '*' or '*.html'

example:

replace_in_tree 'Author: Bill Gates' 'Author: Larry Wall' '*.html'
"

exit
fi

find . -name "$3" -type f | xargs -n 255 perl -pi.bak -e 's/\Q$1\E/$2/
+g'
[download]

Update: I forgot to mention that your script will probably fail.
The third parameter (*.html) will be expanded by the shell, so perl will have the first filename in $ARGV2 and not the glob.
Therefore I changed the usage to have the third parameter quoted.