# Looping per line of input
some | command | sequence | while read var1 var2; do
  # something here
done

# Reading a file line by line
while read var1 var2 etc; do 
  perform --commands --with $var1 $var2 $etc
done < some-file.ext

# The for loop with test syntax
for f in *; do 
  if [[ -d "$f" ]]; then
    pushd "$f";
    echo "Do work";
    popd;
  fi; 
done

# Test for a pattern match
[[ $some-var =~ ^(some|regex)$ ]] && echo "Yep, it's a match!"

# Process substitution: http://tldp.org/LDP/abs/html/process-sub.html
cat <(what magic is this?)

# Load an array with data
# http://unix.stackexchange.com/questions/99423/appending-to-same-array-in-various-loops-only-last-values-remain-bash-4
some_array=()
while some test; do
  some_array+=("$some_variable")
done < <(some command producing output)

# if __name__ == '__main__': equivalent
if [[ ${BASH_SOURCE[0]} != $0 ]]; then
  # We were sourced, not run
else
  # We are being run, go, go, go!
fi