Beefy Boxes and Bandwidth Generously Provided by pair Networks
Pathologically Eclectic Rubbish Lister
 
PerlMonks  

Re^2: Breaking The Rules

by Anonymous Monk
on May 31, 2006 at 20:00 UTC ( #552920=note: print w/ replies, xml ) Need Help??


in reply to Re: Breaking The Rules
in thread Breaking The Rules

Your two ways of testing undef don't actually do the same thing. if defined $var will execute your statement if $var is defined. unless $var eq undef will execute your statement if $var is undef, the empty string, or something else that will stringify to the empty string. Try the following code snippet to see for yourself:

my $var = undef; print "Undefined!\n" if $var eq undef; $var = ''; print "Undefined again!\n" if $var eq undef;
This happens because the "eq" operator stringifies both of its arguments, and undef stringifies to the empty string. The warning doesn't exist just to critique your syntax... it's warning you of a danger that your code might not be doing exactly what you think it is.


Comment on Re^2: Breaking The Rules
Select or Download Code
Re^3: Breaking The Rules
by Unanimous Monk (Sexton) on May 31, 2006 at 22:15 UTC
    Hmmm, your right. Thatís not how I thought it was working, but it makes sense that it works that way.

    Learn something new everyday! (I apologies if this is what GrandFather was trying to point out, and I was too obtuse to realize it) :)

Log In?
Username:
Password:

What's my password?
Create A New User
Node Status?
node history
Node Type: note [id://552920]
help
Chatterbox?
and the web crawler heard nothing...

How do I use this? | Other CB clients
Other Users?
Others about the Monastery: (7)
As of 2014-12-25 14:06 GMT
Sections?
Information?
Find Nodes?
Leftovers?
    Voting Booth?

    Is guessing a good strategy for surviving in the IT business?





    Results (160 votes), past polls