The input:

my $foo = $bar;
print "hi $foo\n";
print 'hi ', $foo, "\n";
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...stored in very-easy-print-interpolation2.pl

Run, thusly:

ppi_dumper very-easy-print-interpolation2.pl
[download]

ppi_dumper is in App-PPI-Dumper.

The output:

PPI::Document
  PPI::Statement::Variable
    PPI::Token::Word    'my'
    PPI::Token::Whitespace      ' '
    PPI::Token::Symbol          '$foo'
    PPI::Token::Whitespace      ' '
    PPI::Token::Operator        '='
    PPI::Token::Whitespace      ' '
    PPI::Token::Symbol          '$bar'
    PPI::Token::Structure       ';'
  PPI::Token::Whitespace        '\n'
  PPI::Statement
    PPI::Token::Word    'print'
    PPI::Token::Whitespace      ' '
    PPI::Token::Quote::Double   '"hi $foo\n"'
    PPI::Token::Structure       ';'
  PPI::Token::Whitespace        '\n'
  PPI::Statement
    PPI::Token::Word    'print'
    PPI::Token::Whitespace      ' '
    PPI::Token::Quote::Single   ''hi ''
    PPI::Token::Operator        ','
    PPI::Token::Whitespace      ' '
    PPI::Token::Symbol          '$foo'
    PPI::Token::Operator        ','
    PPI::Token::Whitespace      ' '
    PPI::Token::Quote::Double   '"\n"'
    PPI::Token::Structure       ';'
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This demonstrates that PPI does not handle interpolation in a print statement very well, but a print statement with a list does work.