Oh yes, Devel::NYTProf is a fantastic tool!

Just for completeness, you can examine the OP codes generated for different snippets of Perl code via B::Terse. For example:

> perl -MO=Terse -e "sprintf '%04d', $_"
LISTOP (0x254e078) leave [1]
    OP (0x2753080) enter
    COP (0x254e0b8) nextstate
    LISTOP (0x254e118) sprintf [2]
        OP (0x254e158) pushmark
        SVOP (0x254e1f8) const [3] PV (0x254f200) "%04d"
        UNOP (0x254e188) null [14]
            PADOP (0x254e1c0) gvsv  GV (0xd6af50) *_
-e syntax OK

> perl -MO=Terse -e "qq{$i$j$k$l}"
LISTOP (0x2806210) leave [1]
    OP (0x28061e0) enter
    COP (0x2806250) nextstate
    UNOP_AUX (0x28062b0) multiconcat [8]
        OP (0x28062f0) null [3]
        UNOP (0x664fe0) null [14]
            PADOP (0x665018) gvsv  GV (0x65fbb0) *i
        UNOP (0x664f70) null [14]
            PADOP (0x664fa8) gvsv  GV (0x6549e8) *j
        UNOP (0x664ec0) null [14]
            PADOP (0x664ef8) gvsv  GV (0x65ff10) *k
        UNOP (0x2806360) null [14]
            PADOP (0x2806398) gvsv  GV (0x654b68) *l
-e syntax OK

> perl -MO=Terse -e "$i.$j.$k.$l"
LISTOP (0x27d23b0) leave [1]
    OP (0x27d2380) enter
    COP (0x27d23f0) nextstate
    UNOP_AUX (0x27d2450) multiconcat [7]
        UNOP (0x25d2d70) null [14]
            PADOP (0x25d2da8) gvsv  GV (0x25c4d78) *i
        UNOP (0x25d2d00) null [14]
            PADOP (0x25d2d38) gvsv  GV (0x25c49b8) *j
        UNOP (0x25d2c50) null [14]
            PADOP (0x25d2c88) gvsv  GV (0x25d01b0) *k
        UNOP (0x27d2490) null [14]
            PADOP (0x27d24c8) gvsv  GV (0x25c4e38) *l
-e syntax OK
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No great surprise to see qq{$i$j$k$l} and $i.$j.$k.$l generating the same OP codes under the covers.