sub resolve_envs {
    my ($path) = @_;
    while ($path =~ m/[^\\]\$\{?(\w+)\}?/) {
        my $env = $1;
        if (exists($ENV{$env})) {
            $path =~ s/([^\\])\$\{?(\w+)\}?/$1$ENV{$env}/;
        } else {
            $path =~ s/([^\\])\$\{?(\w+)\}?/$1\\\$$env/;
        }
        
    }
    $path =~ s/\\\$/\$/g;
    return $path;
}

##</code><code>##

set playground="${HOME}/playground"
set file1=${playground}'/fi$le1'
set file2=${playground}'/fi\$le2'
mkdir -p ${playground}
touch ${file1}
touch ${file2}