An awk script I threw together to break down strings for explanation in Stack Exchange answers.

breakdown.awk

# 1. Take any string such as this regex \v<[1-9]\d{,2}\ze(\d{3})*>
# 2. Indicate separations with a delimiter char like underscore
# 3. Run awk like so:
#
#    awk -v RS='_' -f {thisfile} <<< '\v_<_[1-9]_\d_{,2}_\ze_(_\d_{3}_)_*_>'

# Result:

#  \v<[1-9]\d{,2}\ze(\d{3})*>
#  \v                         # 
#    <                        # 
#     [1-9]                   # 
#          \d                 # 
#            {,2}             # 
#                \ze          # 
#                   (         # 
#                    \d       # 
#                      {3}    # 
#                         )   # 
#                          *  # 
#                           > # 

# Change the 'RS' value to whatever delimiter char you prefer.

{
    recs[NR] = $1
    full = full $1
}

END {
    printf " %s\n", full
    len = length(full); pad = 1
    for (rec in recs) {
        printf "%*s%-*s# \n", pad, " ", len-pad+2, recs[rec]
        pad += length(recs[rec])
    }
}


# You want it all crushed on a single command-line?
#
# awk -v RS='_' '{ recs[NR] = $1; full = full $1; }; END { printf " %s\n", full; len = length(full); pad = 1; for (rec in recs) { printf "%*s%-*s# \n", pad, " ", len-pad+2, recs[rec]; pad += length(recs[rec]); } }' <<< '\v_<_[1-9]_\d_{,2}_\ze_(_\d_{3}_)_*_>'