That's good defensive programming

It sure is!
Defensive programming can bite you, though. Kane, one of the Rotterdam Perl Mongers once told the story about what happens if you localize $@ in a BEGIN block. By programming defensively, he ran into a bug in perl :)

perl -e'BEGIN { local $@; print "a"; die "b"; print "c"; } print "d";'
[download]

It turns out that the program doesn't die, and it doesn't display "b" (and not "at -e line 1"). The snippet above prints "ad". If it didn't localize $@, it would print:

b at -e line 1.
BEGIN failed--compilation aborted at -e line 1.
[download]

Scary, huh?

If you localize special variables, look out for bugs, and if you find any, report them!

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