% perl -MO=Concise -e 'print "Hello, $world!"'
a  <@> leave[1 ref] vKP/REFC ->(end)
1     <0> enter ->2
2     <;> nextstate(main 1 -e:1) v ->3
9     <@> print vK ->a
3        <0> pushmark s ->4
-        <1> ex-stringify sK/1 ->9
-           <0> ex-pushmark s ->4
8           <2> concat[t3] sKS/2 ->9
6              <2> concat[t2] sK/2 ->7
4                 <$> const[PV "Hello, "] s ->5
-                 <1> ex-rv2sv sK/1 ->6
5                    <#> gvsv[*world] s ->6
7              <$> const[PV "!"] s ->8
[download]

% pugs -c -e 'print "Hello, $world!"'
{ Statements
    [(
        App "&prefix:print"
            [App "&prefix:~"
                [App "&infix:~"
                    [Val (VStr "Hello, ")
                    ,App "&infix:~"
                        [Var "$world"
                        ,Val (VStr "!")
                        ] []
                    ] []
                ] []
            ] []
        ,"<interactive>" (line 1, column 1)
    )]
}
[download]

That should give you a pretty good idea of what an AST is. :)