Perl one-liners
The -e switch lets you run a tiny Perl program straight from the command line.
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Perl one-liners
perl -e followed by quoted code runs it without a file. Useful switches include -n (loop over each input line), -p (loop and print each line), -l (handle newlines for you) and -i (edit files in place). One-liners are popular for quick text transformations in shell pipelines.
Note:
Use -w or put use warnings inside the code to see warnings in one-liners.
Example: Perl one-liners
$ perl -e 'print "Hello from a one-liner\n"'
Hello from a one-liner
$ echo "perl is fun" | perl -pe 's/perl/Perl/'
Perl is fun
$ perl -lne 'print length' words.txt
$ perl -i.bak -pe 's/cat/dog/g' notes.txt⚠️ Run this in your own terminal or Node.js environment.
Common Mistakes
- Forgetting the quotes around the code so the shell splits it
- Mixing up -n (no automatic print) and -p (prints each line)
- Using -i without a backup suffix on files you cannot recover
Chapter Summary
- perl -e runs code from the command line
- -n loops over input lines
- -p loops and prints each line
- -i edits files in place
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