To give a specific example, this Acme::EyeDrops'ed program prints 99 bottles of beer:

    ''=~(        '(?{'        .('`'        |'%')        .('['        ^
+'-')
    .('`'        |'!')        .('`'        |',')        .'"'.        '
+\\$'
    .'=='        .('['        ^'+')        .('`'        |'/')        .
+('['
    ^'+')        .'||'        .(';'        &'=')        .(';'        &
+'=')
    .';-'        .'-'.        '\\$'        .'=;'        .('['        ^
+'(')
    .('['        ^'.')        .('`'        |'"')        .('!'        ^
+'+')
   .'_\\{'      .'(\\$'      .';=('.      '\\$=|'      ."\|".(      '`
+'^'.'
  ).(('`')|    '/').').'    .'\\"'.+(    '{'^'[').    ('`'|'"')    .('
+`'|'/'
 ).('['^'/')  .('['^'/').  ('`'|',').(  '`'|('%')).  '\\".\\"'.(  '['^
+('(')).
 '\\"'.('['^  '#').'!!--'  .'\\$=.\\"'  .('{'^'[').  ('`'|'/').(  '`'|
+"\&").(
 '{'^"\[").(  '`'|"\"").(  '`'|"\%").(  '`'|"\%").(  '['^(')')).  '\\"
+).\\"'.
 ('{'^'[').(  '`'|"\/").(  '`'|"\.").(  '{'^"\[").(  '['^"\/").(  '`'|
+"\(").(
 '`'|"\%").(  '{'^"\[").(  '['^"\,").(  '`'|"\!").(  '`'|"\,").(  '`'|
+(',')).
 '\\"\\}'.+(  '['^"\+").(  '['^"\)").(  '`'|"\)").(  '`'|"\.").(  '['^
+('/')).
 '+_,\\",'.(  '{'^('[')).  ('\\$;!').(  '!'^"\+").(  '{'^"\/").(  '`'|
+"\!").(
 '`'|"\+").(  '`'|"\%").(  '{'^"\[").(  '`'|"\/").(  '`'|"\.").(  '`'|
+"\%").(
 '{'^"\[").(  '`'|"\$").(  '`'|"\/").(  '['^"\,").(  '`'|('.')).  ','.
+(('{')^
 '[').("\["^  '+').("\`"|  '!').("\["^  '(').("\["^  '(').("\{"^  '[')
+.("\`"|
 ')').("\["^  '/').("\{"^  '[').("\`"|  '!').("\["^  ')').("\`"|  '/')
+.("\["^
 '.').("\`"|  '.').("\`"|  '$')."\,".(  '!'^('+')).  '\\",_,\\"'  .'!'
+.("\!"^
 '+').("\!"^  '+').'\\"'.  ('['^',').(  '`'|"\(").(  '`'|"\)").(  '`'|
+"\,").(
 '`'|('%')).  '++\\$="})'  );$:=('.')^  '~';$~='@'|  '(';$^=')'^  '[';
+$/='`';
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Running the above code through perl -MO=Deparse produces:

'' =~ /(?{eval"\$==pop||99;--\$=;sub\n_\{(\$;=(\$=||No).\" bottle\".\"
+s\"x!!--\$=.\" of beer\").\" on the wall\"\}print+_,\", \$;!\nTake on
+e down, pass it around,\n\",_,\"!\n\n\"while++\$="})/;
$: = 'P';
$~ = 'h';
$^ = 'r';
$/ = '`';
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The last four lines above ($: = 'P';...) match your posted code and are just harmless "filler" code, setting a variety of Perl special variables to random values after the eval has already been executed. This filler code is meant to be a "no-op"; its only (cosmetic) purpose is to fully fill all the beer bottles with code. If you don't want the filler code to be inserted, you can set the Acme::EyeDrops FillerVar attribute to '' (see the documentation of FillerVar in the Acme::EyeDrops documentation for the gory details).

If you squint, you'll notice that -MO=Deparse has deparsed the original:

$:=('.')^  '~';
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to:

$: = 'P';
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which is helpful and all that you'll get from Deparse.

Update: You could manually do what Corion suggested by editing the Deparse output, just changing eval to print like so:

'' =~ /(?{print"\$==pop||99;--\$=;sub\n_\{(\$;=(\$=||No).\" bottle\".\
+"s\"x!!--\$=.\" of beer\").\" on the wall\"\}print+_,\", \$;!\nTake o
+ne down, pass it around,\n\",_,\"!\n\n\"while++\$="})/;
$: = 'P';
$~ = 'h';
$^ = 'r';
$/ = '`';
[download]

Running this produces the original source, without the annoying escapes:

$==pop||99;--$=;sub
_{($;=($=||No)." bottle"."s"x!!--$=." of beer")." on the wall"}print+_
+,", $;!
Take one down, pass it around,
",_,"!

"while++$=
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