2 added 12 characters in body

# Perl: 3534 characters

$_="He12o wor3d!\n";s ";s{\d}{l}g;print  Sample run: bash-4.1# perl -e '$_="He12o wor3d!\n";s
> ";s{\d}{l}g;print'
Hello world!


(Not a big deal. Posted just to use at least once in my life s/// with those fancy delimiters.)

# Perl: 35 characters

$_="He12o wor3d!\n";s{\d}{l}g;print  Sample run: bash-4.1# perl -e '$_="He12o wor3d!\n";s{\d}{l}g;print'
Hello world!


(Not a big deal. Posted just to use at least once in my life s/// with those fancy delimiters.)

# Perl: 34 characters

$_="He12o wor3d! ";s{\d}{l}g;print  Sample run: bash-4.1# perl -e '$_="He12o wor3d!
> ";s{\d}{l}g;print'
Hello world!


(Not a big deal. Posted just to use at least once in my life s/// with those fancy delimiters.)

1

# Perl: 35 characters

$_="He12o wor3d!\n";s{\d}{l}g;print  Sample run: bash-4.1# perl -e '$_="He12o wor3d!\n";s{\d}{l}g;print'
Hello world!


(Not a big deal. Posted just to use at least once in my life s/// with those fancy delimiters.)