Re^2: Hash from prompt

Athanasius: Thanks for your quick reply. The information you gave me makes sense. I made the change but I get an error that states: "Use of uninitialized value $fruits in concatenation (.) or string at asstl.pl line 28, <STDIN> line 1. Here is my updated code:

### create a hash
my %fruit_num = ( apple => 3,
                  bananas => 1,
                  oranges => 2,
                  );

### promp the user to enter a key
### use the input to dispaly the value with that key.

print "Which fruit do you whish to query? ";
my $fruit = <STDIN>;
chomp $fruit;

my $fruits = $fruit_num{$fruit};

print "Number of" . $fruit . "is" . $fruits . " \n";
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I have even tried taken out the concatenation on the print line but still get an error. Any help would be appreciated. Randy

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Re^3: Hash from prompt
by Athanasius (Cardinal) on Oct 13, 2014 at 04:37 UTC

You’re welcome. Here is a more robust version of the script which uses exists to test that the fruit entered is present as a key in the hash before trying to access its corresponding value:

#! perl
use strict;
use warnings;

my %fruit_num =
(
    apples  => 3,
    bananas => 1,
    oranges => 2,
);

print "Which fruit do you wish to query?\n";
my    $fruit = <STDIN>;
chomp $fruit;

if (exists $fruit_num{$fruit})
{
    my $fruits = $fruit_num{$fruit};
    print "Number of $fruit is $fruits\n";
}
else
{
    print "No data for fruit '$fruit'\n";
}
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Typical runs:

14:35 >perl 1055_SoPW.pl
Which fruit do you wish to query?
apples
Number of apples is 3

14:35 >perl 1055_SoPW.pl
Which fruit do you wish to query?
guavas
No data for fruit 'guavas'

14:36 >
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Hope that helps,

Athanasius <°(((>< contra mundum Iustus alius egestas vitae, eros Piratica,

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Re^3: Hash from prompt
by rshoe (Novice) on Oct 13, 2014 at 04:35 UTC

Athanasius: I just figured out what I did wrong. I typed in the wrong key. Everything works now. I appreciate all your help. Thank you; Randy

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Re^4: Hash from prompt

by AnomalousMonk (Archbishop) on Oct 13, 2014 at 15:08 UTC

rshoe: Further to Athanasius's reply: It is, in general, a very good idea to be suspicious of and to 'sanitize' (i.e., check, test, validate) input to your program even when the entity generating that input is you.

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