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.