It is usually easier to treat errors and special cases with Perl rather than a regex. In this case, do one field at a time. I do not know the error processing that you need, but this should get you started. 
use strict;
use warnings;
use Test::More tests=>2;

my $raw_path = '$HOME/work_dir/${TOOL_NAME}/$VERSION';
my $required_path = 'home/work_dir/hammer/1.01';

my %env = (         # Dummy hash for testing
    HOME      => 'home',
    TOOL_NAME => 'hammer',
    #VERSION   => '1.01',   # Removed to force error
);

sub resolve_env_in_path {
    my ($path) = @_;
    while ($path =~ m/\$\{?(\w+)\}?/) {
        my $field;
        if( exists($env{$1}) ) {
            $field = $env{$1};
        }
        else {
            warn "Invallid path";
            $field = 'UNSPECIFIED';
        }
        $path =~ s/\$\{?(\w+)\}?/$field/;
    }
    return $path;
};

ok( resolve_env_in_path($raw_path) ne $required_path, 'error expected'
+ );
$env{VERSION} = '1.01';
ok( resolve_env_in_path($raw_path) eq $required_path, 'good' );

[download]
Bill

In reply to Re: How to replace envs in path? by BillKSmith
in thread How to replace envs in path? by ovedpo15

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