Print a number, use Perl as your calculator

You can execute any perl code that you provide on the command line as the value of the -e or the -E flag. The difference between the two is that -E enables all optional features and builtin functions that were added since version 5.10 came out in, well a very long time ago.

The first such extra that we get using -E is the say function.

• print will print the value after it
• say will also print the value after it, but it will also print a newline. \n at the end.

perl -e "print 42"


perl -E "say 42"

Forgetting the -E flag

What happens if you try to use the say function, but mistakenly use the -e flag? You get an error:

$ perl -e "say 42"
Number found where operator expected (Do you need to predeclare "say"?) at -e line 1, near "say 42"
syntax error at -e line 1, near "say 42"
Execution of -e aborted due to compilation errors.

Calculator

You can use perl on the command line as a calculator:

$ perl -E "say 19 * 23"
437

$ perl -E "say 19 + 23"
42

• -e
• -E
• print
• say