How do I validate an alphanumeric string with underscore of a fixed format in Perl

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Hi Team,

I am new to perl script and using regex to validate a user input for fixed format.I have t accept only two formats of string as input.

Format 1# R99.999 {Upto any number but it should start with R and go upto some digits after decimal}

Format 2# ABCHD1234_GHI123_XYZ123_R99.999 {Any character upper and lower case with number and underscores before R99.999 will be there always}

Anything other than that will make script to fail.

What I have tried:

I have written below piece of code but getting error.

#! /usr/bin/perl -w

my $usage = "Usage : $0 <user input is required>

# Validation of user input

if (($dest !~ /^R\d+\.\d/) || ($dest !~ "/^[\w_]+/R\d+\.\d/")){
die "ERROR: $dest is not a valid input";
} esle {
     print " $dest is correct";
}


I got error like-
Search pattern not rterminated at ./MyTest.pl line

Note- if ($dest !` /^R\d+\.\d/)    this works alone to validate input like R99.999 but we need to validate both formats

Posted 26-Aug-20 0:26am

JaanVvk

Updated 26-Aug-20 9:01am

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Peter_in_2780 26-Aug-20 7:42am

if (($dest !~ /^R\d+\.\d/) || ($dest !~ "/^[\w_]+/R\d+\.\d/")){

Just before the second R you have a spurious /

JaanVvk 26-Aug-20 8:08am

So you are suggesting to remove '/' before second R?

JaanVvk 26-Aug-20 8:15am

When I removed it it throws another error like-

if (($dest !~ /^R\d+\.\d/) || ($dest !~ "/^[\w_]+R\d+\.\d/")){

Error- Backslash found where operator expected at near "R\"
Unquoted string "d" may clash with future reserved word
Syntax error near "R".

I need to combine these two regex, so that if any input which negate expected Formats 1 & 2 makes script to fail

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k5054 · Accepted Answer · 2020-08-26T09:01:00

Your logic is backwards. When A != B || A != C then this will evalutate to true unless B == C

A = 2
B = 2
C = 3
A != B  => false
A != C  => true
false || true => true

You want to use && instead.

You also might want to check your regexes:
1) the match expression should not be enclosed in quotes
2) you seem to have a stray backslash before the R in the second clause
3) There's no right-hand anchor ($) for either term, so it will match R99.9a. For example your simple case would be /^R\d+\.\d+$/
4) \w includes the underscore, so you don't need to add it to the character class
5) Although you don't say so, you may need to start the complex pattern with a letter. In this case the pattern should start with /^[A-Za-z]...