Checking whether a value is between two limits: Useless use of private variable in void context

Bloehdian has asked for the wisdom of the Perl Monks concerning the following question:

I simply want to check, whether a numeric value is between an upper and a lower limit using the following one liner:

perl -we 'use strict; my $value=1; my $lower_limit = 0; my $upper_limi
+t = 2; if ( ( $value <= $upper_limit ) && ( $value => $lower_limit ) 
+) { print "the value is in the range!\n"}'
Useless use of private variable in void context at -e line 1.
[download]

Currently it seems that I am kind of blind, since I cannot see what is wrong with the condition. I guess here is somebody out who has better eyes. ;-)

Comment on Checking whether a value is between two limits: Useless use of private variable in void context Download Code

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Re: Checking whether a value is between two limits: Useless use of private variable in void context by Fletch (Bishop) on Dec 11, 2019 at 18:51 UTC
You've got `=>` which is a fancy comma not the greater than or equals operator `>=` (see perlop). This means the second half of your if check is `... ( $value, $lower_limit )` which is why you're getting that warning. The cake is a lie. The cake is a lie. The cake is a lie.	[reply] [d/l] [select]
Re: Checking whether a value is between two limits: Useless use of private variable in void context by haukex (Archbishop) on Dec 11, 2019 at 18:56 UTC
Note B::Deparse can be a useful tool: `$ perl -MO=Deparse -we 'use strict; my $value=1; my $lower_limit = 0; my $upper_limit = 2; if ( ( $value <= $upper_limit ) && ( $value => $lower_limit ) ) { print "the value is in the range!\n"}' Useless use of private variable in void context at -e line 4. BEGIN { $^W = 1; } use strict; my $value = 1; my $lower_limit = 0; my $upper_limit = 2; if ($value <= $upper_limit and $value, $lower_limit) { print "the value is in the range!\n"; } -e syntax OK` [download] Say `perl -MO=Deparse,-p ...` to add parentheses and see the precedence better.	[reply] [d/l] [select]
Re: Checking whether a value is between two limits: Useless use of private variable in void context by Perlbotics (Archbishop) on Dec 11, 2019 at 18:54 UTC
`( $value => $lower_limit )` [download] is somewhat like `( $value , $lower_limit )` [download] which is essentially `( $lower_limit )` [download] making `$value` irrelevant. You don't need the fat comma `=>` but the greater or equal operator `>=` .	[reply] [d/l] [select]
Re^2: Checking whether a value is between two limits: Useless use of private variable in void context by Bloehdian (Beadle) on Dec 11, 2019 at 18:59 UTC
Oh my dear! Nasty typo. Hm, at least I learned new terms: "fat comma" and "fancy comma" THX to all	[reply]