Advent of Groovy code, day 8

Advent8.groovy

// http://adventofcode.com/2017/day/8
def input = '''b inc 5 if a > 1
a inc 1 if b < 5
c dec -10 if a >= 1
c inc -20 if c == 10'''

regs =[:].withDefault{0}
inc = { String key, Integer x -> regs[key] += x }
dec = { String key, Integer x -> inc(key, -x) }

input.readLines().each {
    def match = it =~ /^(\w+) (inc|dec) (-?\d+) if (.*)/
    def (full, reg, op, arg, cond) = match[0]
    def code = "if (regs.$cond) $op('$reg',$arg)"
    evaluate code
}
println "Largest register value: " + regs.values().max()