Question

In a script like the following, is it possible without dropping ‘my’ to effectively declare ‘var’ only once and have it visible outside the BEGIN block?

echo -e "\n\n\n" | \
  perl -lne 'BEGIN { my $var="declared & initialized once" } print $var'

Also, why declaring var without ‘my’ makes it visible outside the BEGIN block?

Answer 1

Place a my $var; before the BEGIN block:

$ perl -le 'my $var; BEGIN { $var = "declared"; } print $var;'
declared

my gives the variable lexical scope, so $var is not defined in your example outside the BEGIN block. Removing the my effectively makes it a global variable, which is accessible across the script after assignment.