Well here are the three you mention in your post:

perl -ne 'END {print $.}' filename

perl -ne 'print if 5 .. 70' filename

perl -lane 'print $F[1]' filename
[download]

"Perl makes the fun jobs fun
and the boring jobs bearable" - me

The only list of one-liners I've seen is one Tom Christiansen posted to clpm several years ago --- here is his list:

# run contents of "my_file" as a program
perl my_file

# run debugger "stand-alone"
perl -d -e 42

# run program, but with warnings
perl -w my_file

# run program under debugger
perl -d my_file

# just check syntax, with warnings
perl -wc my_file

# useful at end of "find foo -print"
perl -nle unlink

# simplest one-liner program
perl -e 'print "hello world!\n"'

# add first and penultimate columns
perl -lane 'print $F[0] + $F[-2]'

# just lines 15 to 17
perl -ne 'print if 15 .. 17' *.pod

# in-place edit of *.c files changing all foo to bar
perl -p -i.bak -e 's/\bfoo\b/bar/g' *.c

# command-line that prints the first 50 lines (cheaply) 
perl -pe 'exit if $. > 50' f1 f2 f3 ...

# delete first 10 lines
perl -i.old -ne 'print unless 1 .. 10' foo.txt

# change all the isolated oldvar occurrences to newvar
perl -i.old -pe 's{\boldvar\b}{newvar}g' *.[chy]

# command-line that reverses the whole file by lines
perl -e 'print reverse <>' file1 file2 file3 ....

# find palindromes
perl -lne 'print if $_ eq reverse' /usr/dict/words

# command-line that reverse all the bytes in a file
perl -0777e 'print scalar reverse <>' f1 f2 f3 ...

# command-line that reverses the whole file by paragraphs
perl -00 -e 'print reverse <>' file1 file2 file3 ....

# increment all numbers found in these files
perl i.tiny -pe 's/(\d+)/ 1 + $1 /ge' file1 file2 ....

# command-line that shows each line with its characters backwards
perl -nle 'print scalar reverse $_' file1 file2 file3 ....

# delete all but lines beween START and END
perl -i.old -ne 'print unless /^START$/ .. /^END$/' foo.txt

# binary edit (careful!)
perl -i.bak -pe 's/Mozilla/Slopoke/g' /usr/local/bin/netscape

# look for dup words
perl -0777 -ne 'print "$.: doubled $_\n" while /\b(\w+)\b\s+\b\1\b/gi'

# command-line that prints the last 50 lines (expensively)
perl -e '@lines = <>; print @lines[ $#lines .. $#lines-50' f1 f2 f3 ..
+.
[download]

Note, I don't find the 'dup words' (second from last) one-liner terribly useful as it stands. You might want to change the -0777 to -000 to give the paragraph (and paragraph number) containing the duplicate, or if you want an actual line number so you can jump the start of the offending paragraph then you can fiddle with this one (split across two lines just for readability):

perl -000 -ne '$.=$a+1 and print "$.: doubled <$1> in\n$_\n" 
               if /\b(\w+)\b\s+\b\1\b/gi;$a+=tr/\n//' file
[download]

Does anyone know where I can find things like "counting the lines in a file",

"print lines 5 thru 70 to STDOUT"

or "print the second column"

I was also thinking of writing for myself a couple of "one-liner" utilities. But then, I'm wondering: what is easier/quicker/handier (btw, is handier proper English?) when you want to, e.g. "print lines 5 thru 70 to STDOUT"?:

• Just type:
  cat whatever | perl -ne 'print if 5..70'
  
• Write a perl script that does exactly that and nothing more, stuff it into some directory, and then try hard too remember how it's called, where it is and how it works, when you need it. IMHO, you'd be better off typing the whole one-liner.

Still, a kind of Cookbook dedicated to one-liners might be helpful, not for copy'n'pasting the recipes "as is", but merely as a source of inspiration.

My € 0.02

--bwana147