Are there huge time savings
In this case, absolutely none. Both forms are compiled down into constant strings:
- Double quoted:
% perl -MO=Concise -e 'print qq{hello, world}'
6 <@> leave[1 ref] vKP/REFC ->(end)
1 <0> enter ->2
2 <;> nextstate(main 1 -e:1) v ->3
5 <@> print vK ->6
3 <0> pushmark s ->4
4 <$> const(PV "hello, world") s ->5
-
versus single quoted:
% perl -MO=Concise -e 'print q{hello, world}'
6 <@> leave[1 ref] vKP/REFC ->(end)
1 <0> enter ->2
2 <;> nextstate(main 1 -e:1) v ->3
5 <@> print vK ->6
3 <0> pushmark s ->4
4 <$> const(PV "hello, world") s ->5
-e syntax OK
The compiler will also fold things like "hello, world\n" and 'hello, world' . "\n" into the same constant strings. It's only when interpolation in a double string comes into play that things change:
% perl -MO=Concise -e 'print qq{hello, $world\n}'
a <@> leave[1 ref] vKP/REFC ->(end)
1 <0> enter ->2
2 <;> nextstate(main 1 -e:1) v ->3
9 <@> print vK ->a
3 <0> pushmark s ->4
- <1> ex-stringify sK/1 ->9
- <0> ex-pushmark s ->4
8 <2> concat[t2] sKS/2 ->9
6 <2> concat[t1] sK/2 ->7
4 <$> const(PV "hello, ") s ->5
- <1> ex-rv2sv sK/1 ->6
5 <$> gvsv(*world) s ->6
7 <$> const(PV "\n") s ->8
-e syntax OK
... which is only slightly different to...
% perl -MO=Concise -e 'print qq{hello, } . $world . qq{\n}'
a <@> leave[1 ref] vKP/REFC ->(end)
1 <0> enter ->2
2 <;> nextstate(main 1 -e:1) v ->3
9 <@> print vK ->a
3 <0> pushmark s ->4
8 <2> concat[t4] sKS/2 ->9
6 <2> concat[t2] sK/2 ->7
4 <$> const(PV "hello, ") s ->5
- <1> ex-rv2sv sK/1 ->6
5 <$> gvsv(*world) s ->6
7 <$> const(PV "\n") s ->8
-e syntax OK
The above both amount to much the same thing. So basically, you can always use double quotes, interpolate when you need to, and do not worry about performance.
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