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Re: Perl: last evaluated value as a returned value for a subroutine. See inside

by blue_cowdawg (Monsignor)
on Feb 21, 2013 at 17:15 UTC ( #1019986=note: print w/replies, xml ) Need Help??

in reply to Perl: last evaluated value as a returned value for a subroutine. See inside

I modified your code a bit so you can see what's happening:

use strict; my $R; my $i=1; sub mySub { printf "\n\n%d. R = \"%s\"\n",$i++,$R; unless ($R) { print "CONDITION WORKS\n"; $R = 'some string'; } } print mySub(); #prints CONDITION WORKS\nsome string print mySub(); #prints some string print mySub(); #again
This ends up producing this for an output:
1. R = "" CONDITION WORKS some string 2. R = "some string" some string 3. R = "some string" some string
On the first iteration $R is undefined and there for in a "false" state. Therefore your print inside the "unless" gets executed and an assignment gets performed on $R. Where it gets trickier is the next iterations. Since you have unless($R) as the last evalutation the value of $R becomes the return value for the sub since you didn't specify one. see sub and search for "return" if you want more on this.

Peter L. Berghold -- Unix Professional
Peter -at- Berghold -dot- Net; AOL IM redcowdawg Yahoo IM: blue_cowdawg

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[erix]: I like Coptics :)
[LanX]: Copts
[erix]: sorry - just pulling your leg
[robby_dobby]: erix: It's a little late for that :-)
[robby_dobby]: I was falling asleep at my chair and threw out that one bit about participating in a YAPC. Things went from there :-)
[erix]: never too late to pull legs
[LanX]: Official YAPC Africa 2013 Announcement
erix always game to pull legs from sleeping cells
[erix]: hm nice might do a spot of diving - Red Sea is said to be beautiful
[LanX]: well too many terrorist tourists

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