#!/usr/bin/perl
use strict; use warnings;

my %replace = (
    x=>"xSS*exp",
    y=>"ySS*exp",
    c=>"cSS*exp",
    k=>"kSS*exp",
    a=>"aSS*exp",
    h=>"hSS*exp",
);

while (<DATA>) {
    s/\s+$//;
    print $_, " --> ", plonk($_), "\n";
}

sub plonk {
    my $exp = shift;
    my $rv = "";
    my @stack;

    while (length($exp)) {
        my ($var, $rest);
        if ($exp =~ /^(\w+)(.*)$/) {
            ($var, $rest) = ($1, $2);
            $var = $replace{$var} if exists $replace{$var};
            $rv .= $var;
        }
        else {
            ($var, $rest) = ( substr($exp,0,1), substr($exp,1) );
            if ($var eq '(') {
                push @stack, $rv;
                $rv = "";
            }
            elsif ($var eq ')') {
                $rv = (pop @stack) . "($rv)";
            }
            else {
                $rv .= $var;
            }
        }

        $exp = $rest;
    }

    return $rv;
}

__DATA__
y = a*(k(-1)^alpha)*(h^(1-alpha))
c*theta*hˆ(1+psi)=(1-alpha)*y
1 = beta*(c/c(+1)*alpha*y(+1)/k+(1-delta))
y = a*(k(-1)ˆalpha)*(hˆ(1-alpha))
k = y-c+(1-delta)*k(-1)
ln(a) = rho*ln(a(-1))+ e